Electrolyte compartments

ICIFM-21SP Monopolar Electrolyzers. Id s EM-21 SP monopolar electrolyzer incorporates stamped electrodes that are 2 mm thick and of a relatively small (0.2 m ) size (50). The electrolyte compartments are created by molded gaskets between two of the electrode plates the electrode spacing is finite and is estabHshed by gasket thickness. The electrode frames are supported from rails and are compressed between one fixed and one floating end plate by tie rods. Inlet and outlet streams are handled by internal manifolds. A crosscut view of the electrolyzer is shown in Eigure 21. As of 1989, ICI had Hcensed 20 plants having an annual capacity of 468,250 t of NaOH. 

Fig. 17.8. Representation of a CE system. (1) Electrolyte compartments, (2) the capillary, (3) detector, (4) power supply, (5) sample carousel, (6) electrodes, (7) thermostatted areas and (8) data workstation.

If both electrodes have to be made of materials, that are available only as foils or sheets or are not machinable, or for example, for materials, such as graphite felt, a cell design like the one in Fig. 9 is not realizable. Inlet and outlet systems have to be integrated in the electrolyte compartments. The parallel-plate and frame design of a laboratory flow-trough cell in Fig. 10 consists of easy-to-produce parts, using the fixing method for PTFE tubes in Fig. 4. 

FIGURE I Representation of a CE system. I electrolyte compartments, 2 capillary, 3 detector, 4 power supply, 5 sample carousel, 6 electrodes, 7 thermostated areas, 8 data workstation. 

Fig. 13.1 Separation unit in a column coupling configuration as used for the analysis of anions in river water 1, sampling block with a 30pL sampling valve 2, terminating electrolyte compartment with a cap (3) 4,...

Pure lipid membranes are electrical insulators with a specific capacitance of 1 tiF/cm, which separate two electrolytic compartments. The conductance of biological membranes is maiifly determined by highly specialized proteins that act as ion chaimels. For supported membranes to mimic the electrical properties of a biological membrane, it is necessary to measure its electrical characteristics. Even very small defects that are not... 

Early experiments in the development of isoelectric focusing, a high-resolution steady-state electrophoresis method, occurred in 1912, with an electrolytic cell that was used to isolate glutamic acid from a mixture of its salts.1 A simple U-shaped cell, such as that used for moving-boundary electrophoresis (Chapter 9), with two ion-permeable membranes equidistant from the center, created a central compartment that separated anodic and cathodic chambers, as shown in Figure 11.1. Redox reactions occurring in the anodic (Eq. 11.1) and cathodic (Eq. 11.2) electrolyte compartments generated H+ and OH ions in the respective chambers ... 

Operating Conditions. Voltage vs. current relationships for three types of cells provided with DAP, electrocatalytic cathodes, electrolytic compartments having 3-mm gaps, and turbulence promoters are given below ... 

The three relationships apply to current densities up to 3000 A/m. The DAP assembly comprises a hydrogen depolarized anode and a Nafion 117 membrane the electrolytic compartments are limited by Nafion 324 and Selemion AAV ionexchange membranes. The relationships further apply to operating temperatures of 60 - 70 °C and to 13-18% caustic soda, 200-300 sodium sulfate, and 10% sulfuric acid. 

These general considerations must, in any case, take into account both the kind of electrolysis and the structure of the cells (two or three electrolyte compartments). In the first case, the sulfate solution is strongly acid and high levels of impurities are allowable. Besides, the electrolysis cell is inserted in an open cycle where the accumulation of impurities is negligible. 

Electrolyte enters from the side near the bottom of two rigid, plastic end blocks supporting the stack and exists from the diagonal top sides. The two electrolyte compartments are fed independently. When running the cell the center (electrolyte) compartment is overpressured by one psi, thus forcing the membrane to lie against the electrode screening. 

The volume of the electrolyte solution was kept at 10 1 + 6% throughout the run when necessary by direct addition of hot water to the electrolyte compartment. 

The electrolyte was circulated at a rate of about 3 gal/min from the ceU to the storage tank from which it was fed to the circulating pump. After leaving the pump, it passed through the steam-jacketed heat exchanger where it was heated (or cooled with tap water) according to the temperature desired in the ceU and returned to the inlet of the electrolyte compartment. A sidestream of electrolyte was cooled and circulated through a cooler to the pH ceU. Thus, all pH measurements were measured at about 25°C. 

When all the cell compartments are full and water is running down the drain the circulation rate is increased to 0.1-0.2 gal/min in the anolyte and catholyte compartments and 2-2.25 gal/min in the electrolyte compartment. 

These circulation rates give about a one psi difference between the electrolyte compartment and the anolyte and catholyte compartments. The difference is required to keep the membranes apart and against the membrane screens, thus maintaining a constant distance between membranes. 

The Nemst equation (Section 7.6.2) was presented as an equation valid for redox electrode processes in electrochemistry. The Nemst concept is also used for the calculation of die potential difference across a membrane that separates two electrolyte compartments with different ion concentrations. Exchanging the natural logarithm with the common logarithm and putting n = 1 and temperature 37 °C, Eq. 7.9 becomes ... 

Fig. 8. Schematic diagram of a measuring head 1) = Membrane film 2) = Electrolyte compartment 3) = Cathode 4) = Anode (ring-shaped)...

To study these phenomena, one measures the hydrogen permeability of a metal as a function of chosen variables using a two-compartment electrochemical cell schematically shown in Figure 11.30. The working electrode, in the form of a thin sheet, separates the two electrolyte compartments. In the cell s left-hand compartment, the electrode acts as a cathode. When a small, constant current is applied, the protons are reduced to hydrogen. A fraction of this hydrogen dissolves in the metal and diffuses across the thin sheet. 

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